Safety apparatus for grinding machine



April 1964 SHIGEKICHI MIYABAYASHI 3,

SAFETY APPARATUS FOR GRINDING MACHINE Filed 001;. 5, 1962 a E F INVENTOR M /Qb 4745A United States Patent O SAFETY APPARATUS FOR GRINDING MACHINE Shigekichi Miyahayaslii, Nagoya-phi, Aichi-ken, Japan, as-

signor to The Nippon Told Keisha Ltd., Nagoya-shi,

Aichi-ken, Japan, a corporation of Japan Filed Oct. 5, 1962, Ser. No. 228,661 Claims priority, application Japan Oct. 10, 1961 1 Claim. (Cl. 51134.5)

In grinding operation with a grinder wheel, when a grinder wheel has become worn, it has a diameter smaller than its original size. Accordingly when it is rotated at the same rotation speed as that at the time of the initial operation, that is, when it has a greater diameter, its peripheral speed becomes too low and the consumption of the grinder wheel is made great. In order to avoid this disadvantage, when the diameter of the grinder wheel becomes small, the peripheral speed of the grinder wheel is maintained at a rate as required by increasing the rotation speed by means of a change gear. In this condition, the grinding operation is carried out until the grinder wheel becomes unusable. Then the worn out grinder wheel is replaced by a new one which has great diameter of original size. In this case, if the grinding operation is carried out at the same rotation speed as before, the peripheral speed of the new grinder wheel is too great and it results in lowering its grinding efficiency. Furthermore, it is dangerous. The change of the rotation speed of the grinder wheel according to its diameter is therefore important. Nevertheless it is often overlooked and causes accidents.

The present invention relates to an apparatus for securing the prevention of excessive high speed of a grinder wheel and is characterized in that the rotation speed of a grinder wheel is necessarily changed to a speed as required when it is replaced so that excessively high peripheral speed of a grinder wheel will be prevented. The invention will be explained hereinafter with reference to one of the embodiments thereof as illustrated in the attached drawings, in which:

FIG. 1 is a front view of the apparatus of the present invention, partly in section, showing essential elements thereof; and

FIG. 2 is a side view of same.

A main shaft 2 having a grinder wheel 1 fixed at its left end is mounted in the lower part of a gear box 3. A slidable gear body 4 is mounted on a spline shaft 8 which is rotatably mounted on the upper part of the gear box 3. The slidable gear body 4 has a gear 5 of a greater number of teeth on the right and a gear 6 of a smaller number of teeth on the left and these two gears are connected by a ring which forms a recess 7 between the two gears. The gears and the ring are made integral to form the gear body 4 which is mounted slidably in the axial direction on the spline shaft 8. Askant below the spline shaft 8, a driven shaft 11 is mounted in the gear box 3. On this shaft 11, a gear 9 is keyed in such a position as it comes in engagement with the gear 5 of the gear body 4 when the latter is shifted to the right while a gear 10 is keyed in such a position as it comes in engagement with the gear 6 of the gear body 4 when the latter is shifted to the left as shown in FIG. 1.

A lever shaft 12 is mounted horizontally in the cross direction below the spline shaft 8, and it has a fixed change gear arm 13 of U form which fits in the ring recess 7 of the gear body 4 by its inwardly bent ends on both sides as shown in FIG. 2. Said change gear arm 13 is provided with a fixed projection 14 which projects downwardly from the left part of the bottom of the change gear arm. On the end of the lever shaft 12 projecting outside of the gear box 3 is fixed a change gear lever handle 15 which is operated to shift the slidable 3,129,534 Patented Apr. 21, 1964 gear body 4 to right or left to bring the gear 5 in en gagement with the gear 9 or the gear 6 in engagement with the gear 10 to change the rotation speed of the grinder wheel 1, the gear ratios of gears 9 and 10 which come in engagement with gears 5 and 6 being designed to give proper rotation speed according to the size of the grinder wheel in use.

A safety pin 16 is projected from the side wall of the gear box 3 to have its one end near the side wall of the grinder wheel 1. This safety pin 16 has a collar 17 and a compression coil spring 18 is mounted between the inside wall of the gear box 3 and the collar 17 so that the safety pin 16 will always be urged inwardly to bring the other end of the pin in contact with the projection 14 of the change gear arm 13. However, as explained later, when the grinder wheel is worn and reduced to small diameter of 1', the safety pin 16 may be shifted to the position of 16' projecting over the outer circumference of the grinder wheel 1' by operating the gear lever handle 15. Since rotation speed of the grinder wheel 1 of the present invention is of two-speed gear system, it is designed to place the safety pin 16 in a position within the radius of a new grinder wheel but outside of the radius of a worn grinder wheel which requires high rotation speed.

V-pulleys 19, 20, 21 and 22 are respectively keyed at the ends of the shaft of a prime motor M, the spline shaft 8, the driven shaft 11, and the main shaft 2, and V-belts 23 and 24 are arranged respectively to establish transmission between pulleys 19 and 20 and between pulleys 21 and 22.

The operation of the apparatus of the present invention is as follows.

When the grinder wheel 1 has great diameter, the gear 6 of the slidable gear body 4 is brought in engagement with the gear 10 on the driven shaft 11. Then the rotation of the motor M is transmitted through the V-belt 23 to the spline shaft 8 and then the rotation of the spline shaft 8 to the main shaft 2 through the gears 6, 10, and the V-belt 24 to execute the grinding operation. On the other hand, when the operation is to be carried out with a worn grinder wheel 1 which has small diameter as the result of long use, the change gear lever 15 is operated to the right to slide the slidable gear body 4 on the spline shaft 8 thereby discharging engagement between the gears 6 and 10 and establishing engagement between the gear 5 having teeth of a great number and the gear 9 having teeth of a small number to increase the rotation speed of the grinder wheel 1' to give required peripheral speed. In this operation, the projection 14 of the change gear arm 13 pushes the safety pin 16 to the left against the spring 18 thereby bringing the outer end of the safety pin 16 to a position 16' over the outer circumference of the grinder wheel 1' of small diameter as shown in the drawing.

When the grinder wheel 1' is used further until it becomes unusable and it is to be replaced for a new one, it is impossible to fix a grinder wheel 1 of great diameter to the main shaft 2 because of the presence of the safety pin 16 projecting to the position of 16' unless the safety pin 16 is retired by restoring force of the spring 18 by turning the change gear lever 13 to the left. When the change gear lever 13 is turned to the left, the gear 5 is disengaged from the gear 9 and instead the gear 6 comes into engagement with the gear 10 to give the rotation speed suitable at the time of the use of a grinder wheel of great diameter thereby to give required peripheral speed. Thus it is made possible to execute grinding operation.

As described above, according to the present invention, a safety pin 16 is associated with the change gear mechanism in such a way as to make it impossible to fix a grinder wheel of great diameter by means of the safety pin projected to prevent the fixing so long as the condition of the rotation speed for a grinder wheel of small diameter is left as it is. It is therefore absolutely necessary to operate the change gear lever 15 to change the rotation speed to that suitable for a grinder wheelof great diameter before the fixing of a grinder wheel of great diameter.

Accordingly, the peripheraltspeed of a grinder wheel will never be made too high. Thus all risks pertaining to excessive high-speed are eliminated. According to the present invention, the speed of the grinder wheel is changed according to its diameter. Accordingly satisfactory grinding operation can always be performed with required peripheral speed and operation efiiciency can be promoted by using grinder wheels usefully at high efiicieney until they are exhausted.

I claim:

In a grinding machine, a gear box, a vertical grinding wheel rotatably mounted on said box, a driven shaft with at least two gears thereon operatively connected to said wheel to rotate it, a splined drive shaft with an integrated gear body slidably mounted thereon for engaging one of said two gears at one time, and the other of said two gears at another time to vary the speed of said wheel, a motor drive operatively connected to said splined shaft to drive it, a lever shaft, a gear change lever arm for sliding said gear body on said splined shaft pivotally connected to said lever shaft to swing in a vertical plane, said arm having an upper end adapted to engage said gear body and a lower free end, a horizontal safety pin with an outer end adapted to intercept the vertical plane of said Wheel and an inner end adapted to engage the lower free end of said arm, biasing means urging said inner end against said lower end, and handle means operatively connected to said lever arm to simultaneously pivot its upper end in a direction away from said wheel and its lower end toward said wheel to position the pin outer end across the outer circumference of said wheel.

References Cited in the file of this patent UNITED STATES PATENTS 

